@Barncore
You will need a set (2 cables) of
TS Male (No need for TRS if you're going unbalanced anyways) to
RCA Male to go from your Antelope to your Headphone amp.
Like this :
You will then need a set (2 cables) of
RCA Male to
XLR ( Male or female depending on your monitors input)
Like this:
(XLR Females have holes, XLR Males have schlongs for a triple treat baby , all night looooong !!! Lets go !!)
To resume:
2 x TS Male into Monitor L + R of your Antelope.
Into RCA Male Input R (6) + L (7) of your Topping L30 II
Then you'll go from your L30 II RCA Output ( 2 x RCA Male ) to your Monitors input (I bet those are 2 x XLR Male)
You will not have any signal degradation unless your cables are covering great distances (we're talking over 16 feets) or that your room is suffering from very rare and bad interference (think old cellphone waves or an old fart using an AM radio or Short Wave radio close to where you live ) . In the later case, you would need to get a good set of shielded cables but if you're not living in a slum, you will be just fine with any generic cables as long as they are not of the extreme cheap type.
Now if you're into the esoteric part of hifi, I suggest buying yourself a few different sets of 300-400$ cables and a bag of shrooms and letting us know how different they sound.
Hope that help.
EDIT:
Just to be clear, it is best practice to keep your connection in between devices as clean as possible, meaning that if you can ( and yes you can seeing your interface outputs and line outs ) you should used them separately. So keep your Interface connected to your Monitors directly and use a set of Line Outputs and connect it to your Headphone amps. Same thing, 2 cables that go TS Male to RCA Male. No need for the second set of cables. You will then need to switch outputs on your Antelope whenever you want to listen to your cans. (Switch from Monitor Outputs to Line out.)